A compact image pickup apparatus mounted on a mobile phone is required to meet the requirements for compact configuration, low cost and enhanced function. The enhanced function can be achieved by incorporating an “auto focus functions” and “image shake correction functions” realized in a digital camera. In the conventional digital camera, an actuator best suited to each function has been independently developed and adopted.
For example, a voice coil motor using magnetic force and a linear actuator (SIDM=Smooth Impact Drive Mechanism) using an piezoelectric element as a drive source are used for the auto focus function, while shape memory alloys (SMA) are used for image shake correction function.
In the camera module mounted on a mobile phone, an actuator is formed on a substrate, on which an image sensor is mounted, so as to ensure compact configuration (e.g., Unexamined Japanese Patent Application Publication No. 2003-204470). In the lens holder of an optical pickup apparatus, a technique of integral formation of a focus and tilt support mechanism is proposed (e.g., Unexamined Japanese Patent Application Publication No. H10-106013).
However, the proposal of the Unexamined Japanese Patent Application Publication No. 2003-204470 is restricted to the image shake correction function. For example, a separate actuator must be provided to implement auto focus function. In the proposal made in the Unexamined Japanese Patent Application Publication No. H10-106013, two actuators are separately used for focusing and tilting, although the support mechanism is integrally built. Such extra small equipment as a mobile phone has a plurality of different actuators mounted thereon, although each of them is downsized, and hence big problems remain to be solved in the phase of size, ease of assembling and adjustment and production cost.
In the meantime, a polymer actuator is currently capturing the spotlight because of increased force, reduced weight, minimized noise, low voltage drive, and formation in a desired shape due to the material of resin.
In this context, a proposal has been made of a drive section of the correction apparatus in an image pickup apparatus provided with an image shake correction function that can be embodied by using a polymer actuator as a drive source (e.g., Unexamined Japanese Patent Application Publication No. 2005-330457).
Another proposal is a technique of eliminating the distortion of an image by bending an image pickup device in a convex form, using a polymer actuator as a drive source (e.g., Unexamined Japanese Patent Application Publication No. 2005-278133).
However, the proposal disclosed in the Unexamined Japanese Patent Application Publication No. 2005-330457 merely describes that the polymer actuator is preferably used in the drive section of the correction apparatus in an image pickup apparatus provided with image shake correction function, without mentioning any specified means or method. Further, although this is not directly related much to the present invention, it should be pointed out regarding the method proposed in the Unexamined Japanese Patent Application Publication No. 2005-278133 that, if external force is applied so as to bend a semiconductor element such as an image pickup device in a convex form, a crack of the element will occur, or element characteristics will be subjected to a change due to deflection, with the result that deterioration of characteristics will be caused.
Further, when the auto focus function or image shake correction function is to be performed by moving the image pickup device in the direction parallel or vertical to the optical axis, not only the image pickup device but also the circuit board with the image pickup device mounted thereon must be moved. This involves a problem of moving a large and heavy object.